Wellscreen having helical support surface

ABSTRACT

A method and apparatus for assembling a wellscreen onto a perforated base pipe are provided. The wellscreen defines a tubular body which is suitable for subterranean use in oil, gas, and water wells. In accordance with the present invention, the wellscreen first defines a perforated base pipe having termination members at its opposite ends. Disposed on each termination member is a continuous helical, step-tiered surface. The helical surface serves as a support surface for a layer of filtering material which is rolled around the base pipe. The filtering material is pre-cut to a correct diameter and bias to match the diameters and bias of the spiraling termination support surfaces. The filtering material is connected to the rings to form a substantial seal on the opposite ends. A protective, perforated outer shroud is optionally disposed around the filtering media as well.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to well completion methods. Morespecifically, the present invention relates to an apparatus and methodfor assembling a wellscreen for use in oil, gas, and water wells.

[0003] 2. Description of the Related Art

[0004] Wellbores are typically formed by drilling a borehole into theearth in order to penetrate one or more hydrocarbon-bearing formations.Typically, the wellbore is supported by one or more strings of steelcasing which extend from the surface to a desired depth. An annular areais created between the casing and the borehole, which is filled withcement to further support and form the wellbore.

[0005] Some wells are produced by perforating the casing of the wellboreat selected depths where hydrocarbons are found. Hydrocarbons migratefrom the formation, through the perforations, and into the casedwellbore. In some instances, a lower portion of a wellbore is left open,that is, it is not lined with casing. This is known as an open holecompletion. In that instance, hydrocarbons in an adjacent formationmigrate directly into the wellbore where they are subsequently raised tothe surface, either by production pressure or through an artificial liftsystem.

[0006] One problem typically encountered in connection with productionof downhole fluids is the invasion of aggregate material, includingsand, into the wellbore. Sand production can result in premature failureof artificial lift and other downhole and surface equipment. Sand canalso build up in the tubing to obstruct well flow. In addition, producedsand becomes difficult to handle and dispose at the surface.

[0007] The need to remove aggregates from production fluids exists inmany types of wells, including oil and gas wells, water wells,geothermal wells, and wells for ground remediation. Typical particulatesneeding to be filtered out are sand and clay including unconsolidatedparticulate matter, also known as “formation sand”.

[0008] To control particle flow from unconsolidated formations, wellscreens are often employed downhole. These well screens serve assubterranean particle filters, and are conventionally referred to as“sand screens.” Sand screens have been utilized in the petroleumindustry for some time to remove particulates from production fluids.

[0009] Sand screens are typically tubular in shape and serve as afiltering barrier between a formation and a string of tubing orproduction equipment. Modern sand screens are typically constructed fromthree composite layers. These include a perforated base pipe, at leastone porous filter media wrapped around and secured to the base pipe, andan outer cover. The filter media allows hydrocarbons to invade thewellbore, but filters sand and other unwanted particles from entering.

[0010] The sand screen is connected to the lower end of either thecasing or the production tubing. Hydrocarbons travel to the surface ofthe well through the sand screen and via the tubing. Thus, hydrocarbonsor other production fluid are filtered before entering the productionstring and before traveling through expensive production and pumpingequipment.

[0011] A typical method of constructing a wellscreen involves wrappingand seam-welding mesh layers of filtering material around the perforatedbase pipe. The mesh layers typically consist of sintered mesh filterelements and more coarse wire mesh drainage elements. An alternativemethod involves forming a tube of the mesh material, seam welding itlongitudinally, and then sliding it over the perforated base pipe. Aprotective outer shroud consisting of a perforated tube is then placedover the mesh layers and the perforated base pipe.

[0012]FIG. 1 shows a previous version of a perforated base pipe 12 for aprior art well screen 10. The base pipe 12 defines a tubular body havinga plurality of perforations 14 therein. The base pipe 12 includes acentral bore extending from a first end 20A to a second end 20B. At eachopposite end 20A, 20B of the base pipe 12 is a termination member 16.Each termination member 16 defines a series of concentric step-tieredrings 22 having progressively larger diameters. As shown in FIG. 2, thestep-tiered rings 22 of the prior art serve as support members forlayers of filter screen 24 and the protective shroud (not shown) whichwill encompass the base pipe 12 upon completion of the well screen 10.

[0013] A disadvantage to known well screens 10 is the cumbersomemanufacturing process. To assemble the wellscreen 10, the step-tieredrings 22 of the prior art perforated base pipe 12 (FIG. 1) require thatthe layers of filter screen 24 (shown in FIG. 2) be individually sizedto fit each sequential tier on the termination members 22. This meansthat each layer of filter screen 24 must be cut in separate pieces inaccordance with the specific diameter of each corresponding step ring22. After being cut, the layers of filter screen 24 must be separatelywelded to each corresponding step ring 22, starting with the smallestdiameter ring 22′ located at the base of the termination member 16, andmoving up sequentially to each successively larger diameter ring 22until the step ring having the largest diameter 22″ has been fitted fora layer of filter screen 24. This process results in many individualsections of mesh material 24 being separately cut and welded to thecorresponding step-tiered rings 22 of the termination members 16.

[0014]FIG. 2 depicts an intermediate layer of filter media 22 beingapplied to a step ring 22 of a prior art base pipe 12. The step isrepeated for each step ring 22. Thus, in the manufacturing process ofthe prior art, a plurality of layering and welding steps are required.These numerous steps represent a labor-intensive process that is bothexpensive and time consuming. In addition, this process also requires agreater degree of skill from the technicians in manufacturing andmaintenance.

[0015] Therefore, a need exists for a perforated tubular that enablesquicker and easier fabrication welding of filter screen layers to thestep rings. There is a further need for a well screen that enables thefilter layers to be prepared offline for easier assembly at the shop orwell site. In addition, there is a need for a method for assembly of thefilter screen layers onto a helical step-tiered surface in onecontinuous feed welding operation.

[0016] Further yet, there is a need for a method of manufacturing a sandscreen which is less expensive, and which requires less time tomanufacture, assemble, and maintain than known sand screens.

SUMMARY OF THE INVENTION

[0017] The present invention first relates to an improved filteringdevice for filtering particulates from fluid. In the preferredembodiment, the apparatus serves as a wellscreen for filtering sand andother aggregates during production of hydrocarbons from a downholeformation.

[0018] The wellscreen first comprises a perforated base pipe. At eachopposite end of the base pipe is disposed a frustoconical terminationmember. The termination member includes a helical step-tiered surface,which serve as a support for an intermediate filtering media for thewellscreen. Thus, unlike the individual step-type rings of the priorart, the present invention offers an outer spiraling surface. Inaccordance with the present invention, the spiraled step surface forms acontinuous helical pattern, allowing the filtering media to be spooledand attached onto the termination members during manufacturing.Thereafter, an outer protective perforated shroud may optionally beadded.

[0019] The present invention also relates to a method for assembling awellscreen. A pre-slotted base pipe is utilized as the base member forthe wellscreen fabrication. As described above, a frusto-conicaltermination member is disposed at each opposite end of the base pipe.The termination member includes a spiraled step surface, which serves asa support surface for an intermediate filtering layer for thewellscreen. In accordance with the present invention, the spiraled stepsurface forms a continuous helical pattern, allowing a filtering mediato be dispensed and attached onto the termination members in a singleroll.

[0020] The base pipe, including the opposite termination members, ispositioned onto a spool. The filtering layer is then cut and fed througha tensioning roller and attached onto the smallest diameter of thetermination members. Thereafter, the spool is rotated so as to roll thefiltering media onto the tiers of the termination members.

[0021] An outer protective perforated shroud may optionally be added tothe base pipe and filtering media. The filtering media and the outershroud are preferably welded onto the termination members to form asecure containment for the base pipe.

[0022] The completed wellscreen is designed to serve as an inlet portfor production fluids in a downhole wellbore. Accordingly, thewellscreen is positioned in series with a string of production tubingor, in an open-hole completion, a string of casing, downhole. Thewellscreen thus defines a multi-layered tubular, allowing fluids to befiltered and to enter production tubing. In one embodiment, thewellscreen includes a threaded pipe section at least one end tofacilitate the fluid connection of the wellscreen to the productiontubing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] So that the manner in which the above recited features,advantages and objects of the present invention are attained and can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the embodimentsthereof which are illustrated in the appended drawings.

[0024] It is to be noted, however, that the appended drawings illustrateonly typical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

[0025]FIG. 1 is an exploded view of a prior art version of a perforatedbase pipe for a wellscreen. Step-tiered pyramid rings are disposed onopposite termination members.

[0026]FIG. 2 is also a prior art version of a portion of a wellscreen.Visible is a layer of filtering media being placed onto a singlestep-tiered ring.

[0027]FIG. 3 is a plan view of an end of a base pipe of the presentinvention. At the depicted end of the base pipe is a termination memberhaving a helical step surface.

[0028]FIG. 4 is a cross sectional view of a wellscreen taken along line4-4 of FIG. 3.

[0029]FIG. 5 is a perspective view of a wellscreen of the presentinvention being assembled. A base pipe for the wellscreen is shown,having opposite termination members. A filtering media is also shown,ready to be spooled onto the spiraled surfaces residing on thetermination members.

[0030]FIG. 6 is a plan view of the wellscreen of FIG. 5, with thefiltering media being spooled onto the spiraled surfaces of each end.FIG. 6 demonstrates that the filtering media is pre-cut to the correctdiameter for rolling onto the perforated base pipe. In this view, theinitial portion of the filtering media has covered the perforations ofthe base pipe.

[0031]FIG. 7 is a plan view of the base pipe of the present inventionhaving a continuous helical surface on each end. In this view, thewellscreen has been completely rolled onto the base pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032]FIG. 3 is a plan view of an end 70A of a wellscreen 50 of thepresent invention. The wellscreen 50 first includes a base pipe 52having a plurality of slots, or perforations, 54 formed therein. Thediameter and the number of perforations 54 may vary depending on theparticular operation.

[0033] At the depicted end 70A of the base pipe 52 is a terminationmember 66. The termination member 66 is connected to and resides at theend 70A of the base pipe 52. The termination member 66 is generallyfrustoconical in shape, and has disposed thereon a continuous helicalstep surface 72. As will be shown in FIG. 5, the helical step surface 72serves as a support member for an intermediate filtering media 74.

[0034] In accordance with the present invention, the spiraled stepsurface 72 defines a continuous helical pattern. To accomplish this,each of the two helical support surfaces, steps, 72 first has a leadpoint 71A, 71B on a first step-tier 72′. The lead point 71A, 71B is thepoint at which the leading edge 76 of the filtering material 74 isoverlaid onto each termination member 66. Further, each of the twohelical support surfaces 72 has an end point 73A, 73B on a laststep-tier 72″. This is the point at which the trailing edge 80 of thefiltering material 74 is overlaid onto the termination member 66. Thus,each support surface 72 defines a series of outer spiraling supportsteps having a lead point 71A, 71B and an end point 73A, 73B, such thatthe diameter of each termination member 66 grows larger as the helicalsupport surface 72 progresses from the lead point 71A, 71B to the endpoint 73A, 73B.

[0035]FIG. 5 demonstrates that the first step-tier 72′ on thetermination member 66 is positioned closest to the perforations 54 ofthe base pipe 52, and has the smallest diameter. In this respect, thelead point 71A, 71B is proximal to the perforations 54. The laststep-tier 72″ is positioned farthest from the perforations 54 of thebase pipe 52 and has the largest diameter. There is at least onestep-tier 72 intermediate the first 72′ and last 72″ step tiers forminga helical pattern. The helical pattern allows the filtering media 74 tobe spooled onto the termination members 66, either as a single sheet ofmaterial or as a series of spooled sections. Thus, the wellscreen 50 ofthe present invention differs from wellscreens of the prior art 10, inthat the wellscreen 50 of the present invention does not utilizeseparate concentric step-tiered rings 22 for supporting a large numberof separate filtering media 24 layers.

[0036] The perforated base pipe 52 defines a tubular body having aninner bore 58 for transmitting fluids within the wellbore (not shown) tothe surface. In the depiction of FIG. 3, bore 58 in end 70A defines aport for fluid flow. A threaded connector 60A is provided to allow athreaded connection with production string (not shown). In theembodiment of FIG. 3, threaded connector 60A defines a male coupling.However, it is within the scope of this invention to provide awellscreen 50 which is placed in series with the casing (not shown).

[0037]FIG. 4 is a cross sectional view of a well screen 50 taken alongline 4-4 of FIG. 3. The bore 58 of the base pipe 52 is seen centrally.Also visible is the continuous helical step surface 72, starting withthe smallest step-tier 72′, and terminating at the end with the largeststep-tier 72″. In the design for the present invention, the helical stepsurface actually defines a continuous spiral.

[0038]FIG. 5 is a plan view of a wellscreen 50 of the present inventionbeing assembled. The base pipe 52 for the wellscreen 50 is shown, havinga central bore 58 and a plurality of perforations 54. The base pipe 52also includes opposite termination members 66. The entire length offiltering media 74 is also shown, ready to be spooled onto the spiraledrings 72 residing on the termination members 66.

[0039] Both termination members 66 are visible in FIG. 5. Thetermination members are disposed on opposite ends 70A and 70B of thewellscreen 50. In the preferred embodiment, each end 70A, 70B alsodefines a communication member for providing a fluid seal with theproduction tubing (not shown). For example, one end 70A could define themale portion of a threaded coupling 60A (threads shown in FIG. 3), andone end 70B could define the female portion of a threaded coupling(threads not shown).

[0040] Each termination member 66 has a first step step-tier 72′ havinga smallest diameter. The distance between the two first step step-tier72′ is identified as D′. Each termination member 66 also has a laststep-tier 72″ having a largest diameter. The distance between the twosecond step-tiers 72′ is identified as D″. Intermediate each first 72′and last 72″ step-tiers is at least one intermediate step-tier 72. Eachsuccessive step-tier (72′ to 72″) thus increases in diameter as theouter surface of the termination member 66 spirals.

[0041]FIG. 6 is a plan view of a wellscreen 50 of the present inventionbeing assembled. In this view, the perforations of the base pipe 52 forthe wellscreen 50 have been covered by the initial section 77 offiltering media 74. Likewise, the smallest step-tier 72′ has beencovered. However, additional levels of the step-tiers 72 remain to becovered during assembly, including the largest step-tier 72″.

[0042] As can be seen in FIG. 5 and FIG. 6, the filtering layer 74 hasbeen pre-cut to match the diameters and bias of the step surface 72.Thus, the filtering layer at its leading edge 76 has a width of D′,. Thefiltering media then tapers outwardly so that at its trailing edge 80the filtering media has a width of D″. In this arrangement, side edges82A and 82B define a pair of opposite hypotenuse sides which match thehelix angle of the helical support surface. The bias angles of edges 82Aand 82B match the lead angles of the spiral surfaces 72 on terminationmembers 66.

[0043] The filtering media 24 for wellscreens 10 of the prior artconsists of various layers of drainage mesh and filter mesh layeredtogether in an alternating fashion. The filtering layers essentiallydefine sections of sintered and non-sintered mesh. It is noted that thesintering process involves increasing the temperature of the variouscomponents to approximately eighty percent of the melting temperatureand fusing the components together. The respective ends of the filteringmedia layers are wrapped onto corresponding step-tiered rings 22, andwelded or otherwise connected to the termination members 16. Thealternating layers of the various meshes ensure filtering withoutrestricting the flow of fluids into and along the surface of thewellscreen.

[0044] In the wellscreen 50 of the present invention, alternating layers74 of sintered and non-sintered mesh are still employed. The leadsection 77 of filtering media 74 is preferably a non-sintered piece, andis the piece used to attach to the first step-tier 72′. Attachment ispreferably by welding. The base pipe 52 is spooled so as to draw thefiltering media 74 around the perforations 54. As the filtering media 74is spooled, the intermediate helical surface 72 is invoked for support.The intermediate section 78 of filtering media is, in the preferredembodiment, a sintered mesh material. During the spooling process, theside edges 82A, 82B of the filtering media are preferably welded to thehelical surface 72. The filtering media material 74 is sized so that thetrailing edge 80 will cover the last step-tier 72″. Preferably, the lastsection 79 of filtering media 74 is a non-sintered mesh.

[0045]FIG. 7 is a plan view of the wellscreen 50 of the presentinvention after the filtering material 74 has been completely rolledonto the perforated base pipe 52. Trailing edge 80 of the filteringmaterials 74 is visible. Thereafter, an outer protective perforatedshroud (not shown) may optionally be added.

[0046] The present invention also discloses a method for creating awellscreen. According to the present method, a perforated base pipe 52is utilized as the base member for the wellscreen 50 fabrication. Asdescribed above, a frustoconical termination member 66 is disposed ateach opposite end of the base pipe 52. Each termination member 66includes a continuous helical step surface 72, which serves as a supportfor a filtering layer 74 for the wellscreen 50. In accordance with thepresent invention, the helical step surface 72 forms a continuous spiralpattern, allowing a filtering media 74 to be dispensed onto thetermination members 66 in a single roll.

[0047] While it is contemplated that the sintered 78 and non-sintered77, 79 portions of the filtering material 74 would be fabricated into asingle continuous roll, it is within the scope of this invention toprovide separately cut sections of sintered and non-sintered materialwhich would be rolled in proper order. In this embodiment, the filteringmaterial 74 would be a plurality of continuous layers, preferablycomprising alternating sintered 78 and non-sintered 77, 79 sections.

[0048] The base pipe 52, including the opposite termination members 66,is positioned onto a spool (not shown). The pre-cut filtering layer 74is then fed through a tensioning roller onto the smallest step-tier 72′of the termination members 66 from a tensioning roller (also not shown).Thereafter, the spool is rotated so as to roll the filtering media 74onto the rings 72 of the termination members 66.

[0049] An outer protective perforated shroud may optionally be added tothe base pipe 52 and filtering media 74. The filtering media 74 and theouter shroud are preferably welded onto the termination members 66 toform a secure containment for the perforated base pipe 52.

[0050] At this point, the perforated base pipe 52 with spiraling surface72 is now assembled into wellscreen 50 of the present invention, and canbe placed into the appropriate position in the production tubing string(not shown). The completed wellscreen is designed to serve as an inletport for production fluids in a downhole wellbore. Accordingly, thewellscreen 50 is preferably positioned in series with a string ofproduction tubing downhole. The wellscreen 50 thus defines amulti-layered tubular, allowing fluids to be filtered as they enter theproduction tubing. In one embodiment, the wellscreen includes a threadedpipe section at least one end to facilitate the fluid connection of thewellscreen to the production tubing.

[0051] While the foregoing is directed to embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A base pipe for use in a wellscreen, the base pipe comprising: atubular body having a first end and a second end; a plurality ofperforations on said tubular body intermediate said first end and saidsecond end; a termination member disposed on each of said first end andsaid second end; and a helical support surface disposed on each of saidfirst and second termination members defining a support surface forreceiving at least one continuous layer of filtering material.
 2. Thebase pipe of claim 1, wherein each termination member is frusto-conicalin shape; and each helical support surface comprises a lead point on afirst step-tier, an end point on a last step-tier, and at least onestep-tier intermediate said first and last step-tiers such that thediameter of each of said step-tiers grows larger from said lead point tosaid end point.
 3. The base pipe of claim 2, wherein each of saidhelical support surfaces defines a plurality of helical step-tiersintermediate said first and last step-tiers.
 4. The base pipe of claim3, wherein said first step tier is proximal to said tubular body, andsaid last step-tier is distal to said tubular body.
 5. A wellscreen foruse in a wellscreen, the wellscreen comprising: a base pipe defining atubular body having a first end and a second end; a plurality ofperforations on said base pipe intermediate said first end and saidsecond end; a termination member disposed on each of said first end andsaid second end; at least one layer of filtering material disposed aboutsaid base pipe; and a helical support surface disposed on each of saidfirst and second termination members for receiving said at least onelayer of filtering material.
 6. The wellscreen of claim 5, wherein eachtermination member is frusto-conical in shape; and each helical supportsurface comprises a lead point on a first step-tier, an end point on alast step-tier, and at least one step-tier intermediate said first andlast step-tiers such that the diameter of each of said step-tiers growslarger from said lead point to said end point.
 7. The wellscreen ofclaim 6, wherein each of said helical support surfaces defines aplurality of helical step-tiers intermediate said first and laststep-tiers.
 8. The wellscreen of claim 7, wherein said first step tieris proximal to said base pipe, and said last step-tier is distal to saidbase pipe.
 9. The wellscreen of claim 8, wherein said at least one layerof filtering material includes a leading edge which attaches to each ofsaid helical support surfaces at said lead points, and a trailing edgewhich attaches to each of said helical support surfaces at said endpoints.
 10. The wellscreen of claim 9, wherein said at least one layerof filtering material defines a first section of non-sintered porousmaterial, a second section of sintered porous material, and a thirdsection of non-sintered porous material, said leading edge residing onsaid first section of non-sintered porous material, and said trailingedge residing on said third section of non-sintered porous material. 11.The wellscreen of claim 9, wherein said at least one layer of filteringmaterial is substantially fabricated from a sintered screen.
 12. Thewellscreen of claim 10 further comprising an outer, perforatedprotective shroud having a first end and a second end, wherein saidshroud is placed around said sections of filtering material after saidsections of filtering material have been applied to said wellscreen. 13.The wellscreen of claim 12, wherein said first end of said outer,perforated protective shroud is attached to said termination member atsaid first end of said base pipe, and said second end of said outer,perforated protective shroud is attached to said termination member atsaid second end of said base pipe.
 14. A method of assembling filteringmaterial onto a wellscreen for use in a wellbore, the wellscreencomprising: a base pipe defining a tubular body having a first end and asecond end; a plurality of perforations on said base pipe intermediatesaid first end and said second end; a frusto-conical termination memberdisposed on each of said first end second ends of said base pipe; and ahelical support surface disposed on each of said first and secondtermination members, said helical support surfaces serving as a supportsurface for receiving filtering material, and each helical support ringcomprising a lead point on a first step-tier, an end point on a laststep-tier, and at least one step-tier intermediate said first and laststep-tiers such that the diameter of each of said step-tiers growslarger from said lead point to said end point; comprising the steps ofplacing said base pipe upon a spool; cutting a leading edge of saidfiltering material to conform to the distance between said lead pointson each of said helical support surfaces; cutting a trailing edge ofsaid filtering material to conform to the distance between said endpoints on each of said helical support surfaces; cutting said filteringmaterial to taper from said leading edge to said trailing edge in orderto form a pair of opposite hypotenuse sides; which match the helix angleof said helical support surface; attaching said leading edge of saidfiltering material to said lead points on said helical support rings;and rolling said filtering material onto said helical support surfaces.15. The method of assembling filtering material of claim 14, whereinsaid filtering material is rolled onto said helical support surfacesuntil said trailing edge of said filtering material approximatelyreaches said end points on said helical support surfaces.
 16. The methodof assembling filtering material of claim 15, wherein said filteringmaterial is substantially fabricated from a sintered screen.
 17. Themethod of assembling filtering material of claim 15, wherein saidfiltering material defines a first section of non-sintered porousmaterial, a second section of sintered porous material, and a thirdsection of non-sintered porous material, said leading edge residing onsaid first section of non-sintered porous material, and said trailingedge residing on said third section of non-sintered porous material. 18.The method of assembling filtering material of claim 15, furthercomprising the steps of: attaching said trailing edge of said filteringmaterial onto said end points on said helical support surfaces; placinga perforated, outer protective shroud around said sections of filteringmaterial after said sections of filtering material have been rolled ontoand attached upon said helical support surfaces, said shroud having afirst end and a second end.
 19. The method of claim 18, wherein saidstep of attaching said leading edge of said filtering material to saidlead points on said helical support rings includes welding.
 20. Themethod of claim 18, wherein said first end of said outer, perforatedprotective shroud is attached to said termination member at said firstend of said base pipe, and said second end of said outer, perforatedprotective shroud is attached to said termination member at said secondend of said base pipe